The heat dissipating devices for dissipating the heat generated in the power control devices are designed in particular with regard to avoiding excessively large differential voltages between electronic components and the heat dissipating devices, which are thermally and electrically conductive.
Circuit arrangements for electrically controlling power have voltage differences between individual circuit components, such as power semiconductor components, for example, among one another and between components and corresponding heat dissipating devices, such as cooling elements, for example, which voltage differences can reach high values through to breakdown voltages.
In known circuit arrangements, power semiconductor components are arranged on heat dissipating devices which are connected to a ground and are therefore grounded or put at ground potential. Such conventional power control devices for controlling three-phase AC currents and AC voltages are arranged with all the power control modules on a single heat dissipating device, which is clamped or connected to zero volts, such as ground M, for example, as shown in FIG. 1. The circuit arrangement in accordance with FIG. 1 is designed in triple fashion for the power control of three-phase AC currents and AC voltages. The circuit arrangement in FIG. 1 comprises three switching units E1, E2 and E3. The individual switching units E1, E2 and E3 are in turn formed from power semiconductor components T1a, T2a and T3a, T4a respectively connected in series.
A capacitor C1 is discharged via the series circuit comprising two resistors R1 and R2. The other two power control devices E2 and E3 in FIG. 1 are formed in a similar manner. All the power semiconductor components T1a, T2a, . . . , T3c, T4c are arranged on a heat dissipating device W0 for cooling.
Said heat dissipating device W0 has not only a good thermal conductivity but also a high electrical conductivity. During operation of the circuit arrangement, care must be taken to ensure that voltage differences between connection points of the power semiconductor components, on the one hand, and the heat dissipating device W0, on the other hand, do not exceed a specific predetermined maximum potential difference value—that is to say a breakdown voltage.
For solving the problem it has been proposed to provide individual heat dissipating devices W1, W2, W3, W4, W5 and W6 for in each case a pair of power semiconductor components, as shown in FIG. 2. Although such an arrangement avoids large potential differences between all of the power semiconductor components and a single heat dissipating device W0, as shown in FIG. 1, the number of circuit components required is disadvantageously increased.
Disadvantageously, such an arrangement can only be provided for single-component or double-component arrangements. The potential of the corresponding heat conducting device W1-W6 is thus clamped to a centre potential between the two power semiconductor components, which limits the voltage loading to approximately a quarter of the link voltage.
A significant disadvantage of the circuit arrangement shown in FIG. 2 furthermore consists in the fact that such a high number of heat dissipating devices, in the case shown 18 heat dissipating devices for a three-phase system (FIG. 2 shows the circuit components for just one phase), is extremely susceptible to faults and expensive.
Moreover, inexpediently it is not possible to provide such a heat dissipating arrangement for H bridge modules since the latter do not have a common centre potential point. Thus, a solution proposed in accordance with FIG. 2 can reduce the dielectric voltage loading of single-switch packages or dual-switch packages, but disadvantageously a cooling method of this type cannot be used for more recent arrangements such as H bridge modules.
EP 0933 867 A1 specifies a generic electronic circuit arrangement for electrically controlling power, wherein, in FIG. 2b of EP 0933 867 A1 (reference symbols used below refer to EP 0933 867 A1), the heat dissipating device (14) is electrically connected to the power control device (10) and an electrical insulation (13) is disclosed only between the heat dissipating device (14) and cooling fins (0), but not between the heat dissipating device (14) and the power control device (10).
A further generic electronic circuit arrangement for electrically controlling power is specified in EP 0 802 619 A1.